Disk array unit is in general formed of a disk array in which a plurality of magnetic disks are stored and an array controller for reading/writing a magnetic disk stored in the disk array. Because this device structure, when used as a storage system to which a host refers through a network, however, has a shortcoming of poor expandability, frequently used in recent years is a disk array unit in which an array controller and a disk array are managed in the lump as a node basis to have excellent expandability by connecting these nodes.
In the above-described disk array unit formed of a plurality of nodes, some start-up order among nodes often hinders normal initialization processing and accordingly prevents start-up. Similarly, at the time of power-off, normal stop might be hindered by some order of power-off. More specifically, in a disk array unit formed of a plurality of nodes, different timing caused by the order of power-on or power-off in some cases prevents normal start-up or stop of the disk array unit, which is a problem in terms of reliability or data integrity.
Under these circumstances, as disclosed in Patent Laying-Open No. 2002-108573 (Patent Literature 1), known is a disk array unit which executes power-on, power-off and re-activation of a disk developing a fault in order to prevent an originally normal disk from executing degenerate operation when a disk error occurs. Also known, as disclosed in Patent Laying-Open No. 2007-141264 (Patent Literature 2), is a storage system with a switch device provided between a host device and a storage device to realize improvement in storage expandability and reliability according to management information for managing a structure of the storage device.
Patent Literature 1: Japanese Patent Laying-Open No. 2002-108573.
Patent Literature 2: Japanese Patent Laying-Open No. 2007-141264.
The technique disclosed in Patent Literature 1, however, relates to power source control of a disk drive as a single body and not to power source control of entire structure, including an array controller, of a disk array unit formed of a plurality of nodes.
According to the technique disclosed in Patent Literature 2, a switch device in charge of a hub of the Ethernet (registered trade mark) is provided between a host interface and a host adapter having a disk array, which fails to solve the problem of a disk array unit formed of a plurality of nodes whose normal start-up or stop might be prevented due to a difference in timing caused by the order of power-on or power-off as described above.